Question [Q] ZipFile restoring RW, Question about a solution in the dev forum,

at the < HTC Desire 816 > Desire 816 Android Development > [MOD] Restore Pre-4.4.x SD Card Permissions (Writeable) > forum
"bigxie " has an solution to restoring R/W in Android 4.4.2 SENSE 5.5.
He has modified Platform.xml, and this is what I have tried, but as a complete newbee in Android / Linux, my Phone reboots with an error message afterwards.
My Question:
Is it possible to replace the Platform.xml bigxie has incooporated in his zip whit my own Platform.xml, og maybe just edit the existing platform.xml so it could Work with Sense 6?

I need to edit the file and add

<permission name="android.permission.WRITE_EXTERNAL_STORAGE" >
<group gid="sdcard_r" />
<group gid="sdcard_rw" />
<group gid="media_rw" /> (This Line)
</permission>

<permission name="android.permission.WRITE_MEDIA_STORAGE" >
<group gid="sdcard_rw" /> (This Line)
<group gid="media_rw" />
</permission>

and them remove the differences from his and mine XML

If possible any help in explaning how is very much welcome->
Edit (1),
I meant any help in answering this question, I'm familiar with ABD, flashing and sideloading so I doesn't need help explaing how to edit a file, just do I have to use a special program to open and repack the zipfile or will any program like 7z, totalcommander etc be enough to do the job

I've search, and found a lot on how to open Rom's and APKs but nothing about edit or switcing a file in a Zip
My phone HTC DESIRE 816 4.4.2 Sense 6, unlocked, rooted and CWM 6.0.4.7

EDIT (2):
The file from Dev I'm talking about, only has the file Platform.xml inside, the path for the file is the same as the path on my Phone system\etc\permissions, so does antone know if it's possible? if not, are there anywhere I can get sense 5.5 and is it possible to eiter flash or sideload either file?